The fluid that flows through the shell and passes through the set of finned tubes is this supercharging air. The bank also has another fluid flowing through it, which under the circumstances is the fluid used by the circuit that cools the engine, generally a mixture of water and antifreeze.
The shell may be a casing, in general providing a housing open at at least one end, into which the bank is inserted by sliding, in the manner of a drawer. The casing is then closed by a lid in such a way as to make an enclosure, which to cool the supercharging air includes an inlet connection piece and an outlet connection piece for such air; the air arriving via the inlet connection piece passes through the bank in the heat exchanger and can be cooled there.
However, it has been found that the prevailing pressure of the supercharging air in the enclosure is such that the walls of the shell tend to deform, bulging outward, and even to break apart in extreme cases. This problem is further exacerbated by the fact that most often, a plastic shell is used, to reduce the weight and hence the cost.
An attempt to solve this problem has already been made, in particular in U.S. Pat. No. 4,436,145, published on Mar. 13, 1984. In this embodiment, a bank of finned tubes has two water tanks and includes hollow cylindrical sleeves slightly longer than the thickness of the bank and passing all the way through the bank, being disposed at intervals along the bank and parallel to one lateral face of the heat exchanger. The bank is then slid in the manner of a drawer into a casing on a single open side, so as to be assembled with it, in the course of which the ends of the sleeves come into contact with the inside faces of the walls of the casing and act as braces. Corresponding to the cylindrical sleeves, the walls have bores through which screws can be introduced. These screws, via the bores disposed over the first wall, engage the inside of the hollow cylindrical sleeves, passing all the way through the bank of tubes, and discharging via the bores disposed over the second wall, which is parallel to and opposite the first wall. The screw heads rest on the outside face of the first wall, and nuts are screwed onto the shafts of the screws, which extend past the second wall, so as to assure a connection between the two walls of the casing and the bank.
Thus, on the one hand the bank is immobilized in terms of translation in the casing by the sleeves and is blocked in the casing by the screws, and on the other hand, possible deformation of the walls is prevented by these same screws that form tie rods.
Such an embodiment nevertheless has some disadvantages. The hollow cylindrical sleeves must actually be of a major diameter, to be able to withstand the locking effort exerted by the screw and nut. Furthermore, the emplacement of these sleeves on the one hand necessitates occupying a space such that one tube of the bank must be omitted; on the other hand, bores must be provided for receiving the sleeves through this bank, and the bores require that the fins be cut along their length.
Accordingly, this arrangement lowers the capacity of the heat exchanger and also requires additional manipulation to place the screws through the bank and lock them, and these operations entail additional assembly expense.